Pumps and in particular centrifugal pumps are used for pumping pump media, in particular fluids, which enter the pump through a suction pipe and are dispensed by the pump through a pressure pipe. For this purpose, a pump impeller with which the fluid is pumped is arranged within the pump housing. A motor shaft that is connected to the pump impeller is fed outward through the rear wall of the pump housing and can be connected to a motor which, for example, is fastened on the rear wall of the pump.
Such pumps are often also used for pumping corrosive media. For example, they are used for circulating chlorinated swimming pool water. Accordingly, the pumps have to be produced from a corrosion-resistant material or, e.g., have to be protected from direct contact with the pump medium by means of a corrosion-resistant coating.
Corrosion-resistant materials such as, for example, bronze are relatively expensive and difficult to process so that the pumps or pump housings made from such a material are relatively cost-intensive. In contrast, pumps having a coated pump housing can be produced from lower-cost materials such as, for example, gray cast iron, and by using lower-cost production methods.
However, it was found that it is problematic to form a closed corrosion-resistant coating within the shaft passage. In the shaft passage, the seal seat of the mechanical seal arrangement is formed which generally is formed integrally with pump housing. For secure sealing, the mechanical seal seat has to be fabricated in a precisely fitting manner. However, by applying a coating, the required accuracy of fit cannot be ensured.
The consequence of this is that in conventional pumps, the coating is interrupted at least in the region of the seal seat of the mechanical seal arrangement. However, because of this, the seal seat does not represent a rust-proof design. After disassembling the rear wall, for example due to maintenance or repair work, it is often difficult or not possible at all, due to corrosion on the seal seat, to insert a new sealing ring of the mechanical seal arrangement. Hereby, leaks can occur between the seal seat and the new sealing ring. Normally, this results in repair work.